Comparative Study Between a Geothermal Heat Pump System and an Air-to-Water Heat Pump System for Heating and Cooling in Typical Conditions of the European Mediterranean Coast

To make a overall assessment of a Ground Coupled Heat Exchanger (GCHE) it is not only important to understand the behaviour of the GCHE, but also to consider the system in which it will operate: its loads and utilization factors (as a function of climate conditions and application), efficiency (which also depends on the heat pump) and other system parameters, such as pumping requirements, long term soil heat imbalance, etc. As part of the European project GEOCOOL [1], this paper shows the results of applying a methodology developed for the comparative study between a system combining a water-to-water reversible heat pump of commercial size with a vertical GCHE and an equivalent air-to-water heat pump system in typical conditions of the European Mediterranean rim (of great importance for cooling). For this purpose, the seasonal system performance factors for heating and cooling, and the temperature profiles of the water in the GCHE for a 25 year period were calculated for different borehole configurations and for different backfill materials. In addition, an extensive study of relevant climatological parameters of Valencia-Spain was made. These results were transformed into bin-hour data which are used for calculating the seasonal system performance factors for heating and cooling for the air-to-water heat pump system. The heat pump properties have been calculated using the IMST Group’s ART software [2]. Finally, a comparison was made between the GCHE-system and an air-to-water heat pump showing the efficiency improvement obtained for various grouting materials, and for different GCHE geometries. 1